Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 02/07/92

Final Date: 12/16/94

Deleted Date:

Naval Weapons Station (WPNSTA) Concord (also known as Naval Weapons Station Seal Beach Detachment,Concord) is a 12,800-acre site located in the north-central portion of Contra Costa County. WPNSTA Concord is comprised of two geographically separate units, the Inland (5,170 acres) and Tidal (7,630 acres) Areas, and a radiography facility (approximately 1 acre) in Pittsburgh, California. Aside from typical administrative and support work activities, this facility is a major ammunition transshipment port of the West Coast for the Department of Department of Defense, under operation by the Department of Army.

The Navy's Installation Restoration Program (IRP) identified 32 areas potentially containing hazardous substances. The Tidal Area is organized into two site groups or Operable Units that include the Tidal Area Sites and the Litigation Area Sites, and the Army is taking over the responsibility for cleanup from the Navy for this area. The Tidal Area Sites are represented by the Tidal Area Landfill (Site 1), the R-Area Disposal Area (Site 2), the Wood Hogger Area (Site 11), the Froid and Taylor Road Area (Site 9), and the Taylor Boulevard Bridge Disposal Area (Site 30). The Litigation Area is represented by four Remedial Action Sub-Sites (RASSs), that contain the original seven IR Sites (Sites 3, 4, 5, 6, 25, 26, and 28), and geographically includes a recently added Former N-P-K Fertilizer Plant Site (Site 31)(formerly Area of Concern-1). The contamination in the Tidal Area Sites, located in wetlands and low-lying areas in the northwestern portion of the facility, comes from past on-base waste disposal practices, including an estimated 3,000 tons of mixed wastes that were deposited in the landfill from the early 1940s to 1979, material and waste generated during the repackaging of conventional munitions, and chipped wood contaminated with pentachlorophenol (PCP). Investigations identified heavy metals to be the primary contaminants in these sites, but low levels of organochlorine pesticides, such as DDT and its breakdown products, and semi-volatile organic compounds (SVOCs) are also present. The contamination in the Litigation Sites, located in both wetlands and upland habitat on the northeastern portion of the Tidal Area, was the result of private industrial activities on portions of property that was subsequently purchased by the Navy to create a buffer zone for the activity at the facility's piers. Soil sampling that started in 1986 detected metals in these areas. Subsequent testing confirmed this result and expanded the areas impacted. Documented historical releases from industrial operations and tidal action in the wetlands transported and distributed contamination across wetlands and into engineered Mosquito Ditches and Lost Slough, a natural tidal channel. The Tidal Area Sites and Litigation Sites are located in critical habitat for endangered species, such as the Salt Marsh Harvest Mouse and the California Clapper Rail. Suisun Bay supports extensive sport fishing as well as providing habitat for the endangered fish species, Winter-run Chinook Salmon and Delta Smelt.

Other areas of environmental concern are located in the Inland Area, which is still being addressed by the Navy, and include an expanded Site 22 (Building 7SH5 and Main Magazine Area) where elevated arsenic has been detected across wide areas in shallow soils, the Solid Waste Management Units (SWMUs) Sites 2,5,7, and 18, where industrial activity, such as waste storage, has resulted in contamination of soil and groundwater by volatile organic compounds (VOCs), and Former Ordnance Burn and Fire Training Area (Site 13) where low levels of perchlorate have been detected in groundwater and surface water.

In November 2005, WPNSTA Concord was recommended for partial closure and realignment under the Base Realignment and Closure (BRAC) process. The final BRAC determination that was made resulted in approximately half of the facility (Tidal Area) transferred to the Department of the Army in 2008 and the remaining portion (Inland Area) being closed, transferred, and redeveloped.

Contaminants and Risks

Contaminated Media

Groundwater

Surface Water

Soil and Sludges

Environmentally Sensitive Area

Soil, sediments, and surface water are contaminated with heavy metals including zinc, copper, lead, cadmium, and arsenic, as well as SVOC and pesticides. Ingesting or coming into direct contact with contaminated soil, sediments, or surface water may pose a potential health threat. Groundwater has been contaminated at the SWMU Sites above drinking water - Maximum Contaminant Levels (MCLs) and requires cleanup action. Site-specific wetlands and endangered species, such as the Salt Marsh Harvest Mouse and the California Capper Rail, are at risk.

Who is Involved

Investigation and Cleanup Activities

This site is being addressed in two stages: immediate actions and a long-term remedial phase focusing on cleanup of the entire site.

Initial Actions

Immediate Actions: Since 1983, WPNSTA Concord has excavated contaminated soils from the Litigation Area and disposed of them offsite. In addition, WPNSTA Concord performed wetlands restoration activities. Replanting of the site was completed in fall 1995.

Remedy Selected

Tidal Area Landfill (Site 1) Record of Decision was signed by the U.S. EPA on May 17, 2004, and documents the selection of a California Title 27 municipal solid waste muti-layer prescriptive soil cap. Construction of the cap is underway, but has been delayed due to the discovery of munitions within the debris. Because of the munitions, a new landfill cap design is being employed.

Site Studies

Litigation Area Sites Feasibility Study and Proposed Plan have been issued, proposing additional remedial actions necessary to address contaminated aquatic sediments and wetlands soils. The Litigation Area FS was initiated following recommendations contained in a June 2003, Final Five Year Review. The Five Year Review was prepared in response to the Navy's unilaterally signed 1989 ROD which documented the removal of high levels of metals contamination in wetlands soils along with the monitoring of areas with some remaining soil contamination.

Site Studies

Inland Area Site 22 (Building 7SH5 and Main Magazine Area) Supplemental Remedial Investigation was completed in the summer 2004 and it has been determined that the main magazine area (approximately 530 acres) has been contaminated with elevated levels of arsenic, as a result of Navy pesticide and herbicide practices. The Navy has developed remedial alternatives and issued its Proposed Plan.

Initial Actions

Site Studies

Site Studies

WPNSTA Concord is participating in the Installation Restoration Program (IRP), a specially funded program established by the Department of Defense (DOD) in 1978 to identify and investigate military and other DOD facilities. There is a Federal Facilities Site Remediation Agreement (FFSRA) between the Navy and the State of California. The purposes of the FFA are to establish roles and responsibilities of the parties; establish an enforceable schedule for environmental investigations and cleanup actions; and ensure that the Navy will obtain necessary funding for the environmental investigations and actions.

Community Involvement

Public Meetings: The Department of the Navy hosts monthly Restoration Advisory Board (RAB) meetings that are usually held on the first Wednesday of the month at the Concord Police Department (Community Room) at 1350 Galindo Street in Concord, California, 94520. Additional information on the Concord RAB may be obtained by contacting Margaret Wallerstein, RAB Navy co-chair, at (562) 626-7838.